This invention relates to subbases for retrofitting existing pneumatic thermostats and, more particularly, to subbases for providing an adjustable deadband during which the air conditioning plant of a building provides neither heating nor cooling.
Energy conservation requirements have given rise to new standards in room temperature control. For example, 68.degree. F. in winter and 78.degree. F. in summer, rather than a constant year around 75.degree. F., have become the new acceptable control points. With these new control points, the air conditioning equipment which provides both heating and cooling for a building is not controlled in the band between the two control points. Thus, a considerable amount of energy can be saved. In essence, this system provides a fairly large temperature range wherein neither heating nor cooling is being used and the room temperature is allowed to wander within this "deadband" with no control whatsoever.
There are several ways in which such a control function can be obtained. A second thermostat can be added such that the first is controlled around one temperature and the second is controlled around the other temperature to provide the desired deadband. Alternatively, the springs on the heating and cooling actuators can be changed so that these actuators will not be operative to control their respective heating and cooling equipment while the temperature is in this deadband. A still further alternative is to take out the old thermostat and substitute an entirely new thermostat which is capable of providing this deadband function. All of these approaches, however, are expensive not only from the standpoint of the equipment which must be substituted or added to the existing air conditioning plant but also in terms of the amount of field labor required to modify these existing systems.
The present invention minimizes the expense of converting existing air conditioning plants into ones where the temperature is allowed to float within a zero energy band, or deadband, by providing a subbase which modifies the output of the thermostat to provide the desired control. Thus, the subbase divides the thermostat output into three sections--one for heating, one for cooling, and one in which temperature changes result in neither heating nor cooling. When using this subbase, the installer need only disconnect the existing thermostat from the pneumatic tubes in the wall supporting the thermostat, connect the tubes to one pair of nozzles on one side of the subbase, and reconnect the thermostat to a second pair of nozzles on the other side of the subbase.